The Language Acquisition and Language Processing Lab has three eye-trackers: an SR Research EyeLink 1000 remote eye-tracker, a Tobii T120 eye-tracker and a T60 XL wide screen eye-tracker. In addition, the lab hosts state-of-the-art facilities for conducting EEG experiments as well as a host of computer generated experiments with which reaction time data, verbal responses, forced-choice data, and other kinds of data can be gathered.
This is a near-infrared video-based tracking system combined with hyperacuity image processing. It samples pupil location at a rate of 1000 Hz and has a spatial accuracy of less than 0.5°. The Desktop Mount for the EyeLink 1000 system typically sits just below the display that the participant is looking at. Since the EyeLink 1000 camera and the infrared illuminator are near the stimulus display, no electronics need to be near the participant, and any head support can be used.
These eye-trackers consist of a TFT display with an integrated eye-tracker camera that films the eyes. Sources of near infrared light produce reflections of the pupils and cornea. These reflections are used by the system to calculate eye movements and where someone is looking on the display. The advantage of using Tobii is that it measures both eyes and is not overly restricting head movements.
Both EyeLink and Tobii eye-trackers are used for a variety of psycholinguistic paradigms. We use reading and eye-tracking as well as Visual World Paradigm (VWP) with adult participants and VWP and preferential looking experiments with children. Both systems allow us to track participants' eye movements during comprehension to single images or other stimulus material (such as video, animation, or text).
Cognitive processes are the result of electrical activity in neural tissue in the brain. These currents can be measured at the scalp by using electrodes. The resulting signal is called Electroencephalogram or EEG. Voltage changes generated by the brain in response to specific stimuli are much smaller than ongoing spontaneous modulations of the EEG, which is in turn weaker than currents produced by external noise sources (e.g., the power line) or by muscle movements (e.g., of the eyes or jaw). EEG measurements therefore take place in a shielded room, and require participants to minimise movement during the recording. An EEG experiment can last up to 2 hours. Participants will listen to speech or to other auditory stimuli, or will read sentences or look at visual objects presented on the screen. They will moreover perform a task that may require responding to these stimuli. Brain signals are analysed after the recording session using specific mathematical and statistical procedures.